I posted this over in interiors, but figured since it might be specific to the year I should post it here too.

I have a 1964 GMC 1500 longbed stepside. The driver's side door handle was pretty wobbly. (and the window cranked hard, but that's another post)

So I took it apart to check it out.
Here's what I found, a broken assembly in a couple of places.

So I took it apart, fired up the MIG, and melted some metal. Put it all back together... oops, how did that go together again? OK, so I took the passenger side panel off to see (and one there is broken too). Got it all buttoned up, and the door wouldn't open from the inside! After some head scratching I figured it out. I just mounted it as far forward as I could, and that made all the difference. It's like butter now! Here's a pic before I figured it out. Compare that to the first one, and you can see the difference.

Anyway, I figured I'd share this for anyone else who may run across it.

There is one place that you have not looked, and it is there - only there - that you shall find the master.